Lance device with reciprocating drive

ABSTRACT

A lance device comprising a frame, guide and drive connected to the frame for moving the lance in the longitudinal direction relative to the frame. The drive of the lance is a reciprocating drive, allowing stepwise driving of the lance.

The present invention relates to a lance device with flexible lances,such as for example of the type known from the Netherlands patentapplication 1012806 of the same applicant.

Pipe bundles of heat exchangers are cleaned using such a lance device.One or more lances are inserted into a corresponding number of pipes ofthe pipe bundle and fouling in the form of deposits is removed fromthese pipes by water exiting at high pressure at the front of thelances.

In the case of a lance device with flexible lances, the device comprisesa drive which engages on the lance or lances and can drive them forwardinto the pipes and retract them again.

The object of the invention is to further improve such a known lancedevice.

This objective is achieved by reciprocating driving of the lances. Thatis, the lances are driven repeatedly forward and backward over a shortdistance. Driving in the forward direction takes place over a slightlygreater distance than the return driving, so that the lance or lancesgradually move forward.

It has been found that in this manner the efficiency of cleaning of thepipes is greatly increased. Jamming of the lance or lances against harddeposits in the pipe bundles is prevented to a far-reaching extent.

In the context of this application, reciprocating is also understood tomean: pulsating, i.e. driven repeatedly forward through small steps.

In a suitable embodiment the duration of the forward and backwarddriving is adjustable, so that it is possible to adapt to the conditionsand in particular to the seriousness of the fouling of the pipe bundlefor cleaning.

The invention will be further elucidated on the basis of a descriptionof the accompanying pneumatic diagram of an exemplary embodiment.

Standard symbols are used in the diagram shown in FIG. 1, so that thisdiagram is clear to a skilled person and it is possible to suffice witha short description of the operation.

In the diagram of the device 1 two drive motors for the lance drivingdevice are designated with 2. These motors 2 are pneumatic motors whichcan operate in two directions. The operating direction is determined bythe position of valves 6. In the further description the position ofvalves 6, corresponding with a first rotation direction of motors 2, isindicated by A and the second position of valves 6, corresponding with asecond rotation direction of motors 2, is indicated with B.

Motors 2 are fed with compressed air under feeding pressure via lines 3.Further applied are pneumatic control pressures which are supplied vialines 4 and 7.

The pneumatic circuit comprises a shuttle valve 10 with which thedriving can be set to manual control by operating the valve 11, or toautomatic operation by operating the valve 12. It will be apparent thatby operating the valve 11 the control pressure from lines 7, shown onthe right in the figure, acts on the two-way valve 13, whereby thislatter takes up the position shown in the figure and transmits thecontrol pressure from line 4, via line 8, to line 14. When there iscontrol pressure on line 14, the drive can be switched from A to B andback again using shuttle valve 15. When the control member of shuttlevalve 15, which can for instance be embodied as a joystick valve, isoperated such that valve 17 is opened, the control pressure will besupplied via the AND port 19 to control valves 6 such that motors 2 areswitched on in position B.

By operating the shuttle valve 15, whereby valve 16 is activated, thecontrol pressure passes via the AND port 18 to the side of control valve6, whereby the other rotation direction A of motors 2 is switched on. Bysuitable operation of valve 15 the lance can thus be driven in thedirection back and forth.

When shuttle valve 10 is operated such that valve 12 is activated, withthe intention of setting the automatic operating position, the two-wayvalve 13 is set in the position wherein the control pressure fromcontrol lines 17 is fed to line 20. Line 14 herein becomes pressureless,whereby operation of shuttle valve 15 no longer has any effect as aresult of the operation of the AND ports 18, 19.

The control pressure in line 20 is transmitted via line 22 to thetwo-way valve 21. In the drawn position of this valve 21, the controlpressure will then be fed via line 23 to time switch valve 24. Thecontrol pressure is fed simultaneously to control valves 6 such thatthese are set into position A.

After the time period set for time switch valve 24 has elapsed, timeswitch valve 24 opens and the control pressure is fed to a second timeswitch valve 25. After the time set for this valve 25 has elapsed, thecontrol pressure is fed to two-way valve 21, whereby this latter ismoved out of the shown position to the position displaced to the right.

The control pressure is hereby transmitted from line 20, via line 22, toline 30. The control pressure from line 30 arrives via line 31 at timeswitch valve 32 and simultaneously at control valves 6, which therebyswitch to position B, with the associated reversal of the rotationdirection of motors 2.

Here too, after the time set for the time switch valve 32 has elapsed,this valve will open and transmit the control pressure to time switchvalve 33, which opens after the time set for this valve and again feedsthe control pressure via line 35 to two-way valve 21.

The two-way valve 21 hereby switches back to the drawn startingposition, whereafter the pressure is fed once again to line 23, wherebycontrol valves 6 are set in position A and the direction of movement ofmotors 2 reverses once again. The thus described operation is repeatedcontinuously until valve 10 is switched to manual control, or until avalve (not shown) arranged in line 8 is closed.

It will be apparent that the time period in which the motors 2 rotate inthe one direction A corresponds with the total time period set forvalves 24 and 25, and the time period for which the motors 2 rotate inthe opposite direction B is determined by the total of the time set forvalves 32 and 33.

In the shown embodiment the respective time switch valves 24 and 32 canbe bridged with the manually operated valves 26 and 34. The time periodfor direction A is hereby shortened to the time period of valve 25and/or the time period for direction B is shortened to the time periodof valve 33 only.

It will be apparent that with a suitable choice of the switch times forvalves 24, 25, 32, 33 an appropriate reciprocating driving of theflexible lance or lances can be achieved.

It is noted that elements not shown here can be added to the pneumaticdiagram of device 1. It will likewise be apparent that for instance apulsating drive can only be obtained by replacing valve 21 with anon-off valve. Such a possibility can of course be integrated into thepneumatic diagram of the device.

All these variations lie within the reach of the skilled person and mustbe deemed as lying within the scope of the present application.

1. Lance device comprising a frame, guide and drive means comprising atleast one motor connected to the frame for movably guiding and drivingat least one flexible lance in longitudinal direction relative to theframe, wherein the drive means are reciprocating driving of the lance,characterized in that the motor is a pneumatic motor, capable ofoperating in two directions, said drive means further comprising a valveswitching pneumatic pressure to the pneumatic motor such that the lanceis driven in the direction back and forth.
 2. Lance device as claimed inclaim 1, comprising setting means for setting a step size of thereciprocating drive.
 3. Lance device as claimed in claim 1, wherein thesetting means can set a forward step size and a backward step sizediffering therefrom.
 4. Lance device as claimed in claim 3, wherein thebackward step size can be set to zero.
 5. Lance device as claimed inclaim 2, wherein the drive means can drive the lance at a constant speedand the setting means are time period setting means.